1. Field of the Invention
The present invention relates to a seatbelt retractor and a method for assembling a spindle of a seatbelt retractor.
2. Related Technology
A seatbelt device is conventionally attached to a seat of a vehicle so that during a vehicle emergency, such as an emergency stop or a collision in which a large deceleration acts on the vehicle, an occupant is restrained and prevented from being flung forward by inertial force. A seatbelt device includes a retractor disposed behind or inside a seat back. The retractor retracts a webbing (a belt) for restraining the occupant during an emergency using a rotary force while also allowing the webbing to be unreeled freely. Hence, under normal conditions, the webbing remains in close contact with a body of the occupant at all times without slackening, regardless of movement of the occupant.
The webbing is actually retracted by a spindle disposed in the retractor. The spindle is supported to be free to rotate about an axis, and retracts the webbing using force or the like from a spring provided in a retraction spring device, an electric motor, or the like disposed in the retractor. When the vehicle receives a powerful impact during a collision or the like, a pretensioner device provided in the retractor restrains the occupant by locking unreeling of the webbing.
When the body of the occupant is restrained rapidly, however, a great load may be exerted on the body of the occupant via the webbing. To mitigate this excessive load, the retractor is further provided with a load limiter mechanism. During a collision, the load limiter mechanism detects the tension of the locked webbing. When the tension increases beyond a fixed value, an energy absorption member provided in the load limiter mechanism deforms so that a shaft of the spindle rotates in a webbing unreeling direction (a slackening direction). As a result, the webbing is unreeled automatically, thereby lightening the load exerted on the occupant.
To assemble the retractor, typically, as shown in FIG. 6A, a spindle 16 is incorporated by being inserted from an outer side into a circular through hole 14 provided in a side wall of a retractor frame 12. However, an additional component having a larger diameter than the spindle 16, such as a load limiter mechanism 17 (see FIG. 6B) similar to that described above, is attached to an end of the spindle 16, and therefore the spindle 16 cannot be inserted into the circular through hole 14 in the retractor frame 12 from the outer side.
To solve this problem, the diameter of the circular through hole 14 in the retractor frame 12 may simply be increased so that the spindle 16 can be inserted therein. However, a pinion 18 that performs a rotary motion substantially in alignment with the axis of the spindle 16 is disposed on an exterior of the retractor frame 12, and as a result of this rotary motion, the pinion 18 slides while contacting the exterior of the retractor frame 12, as shown in FIG. 7.
When an energy absorption (EA) mechanism (not shown) that unreels the webbing (not shown) by a predetermined length while applying at least a fixed unreeling resistance thereto is operative, the webbing is pulled in a direction of an arrow 19 in FIG. 7, whereby the pinion 18 slides relative to a load bearing 20A (FIG. 6A) formed on the retractor frame 12. When a pretensioner device 26 is operative, on the other hand, the pinion 18 is pulled in a direction of an arrow 21 in FIG. 7 so as to slide relative to a load bearing 20B shown in FIG. 6A.
Hence, the load bearings 20A, 20B for receiving force from the pinion 18 must be formed in the retractor frame 12, and therefore the circular through hole 14 cannot be increased in size. When a retractor frame 32 having a larger circular through hole 34 is used, as shown in FIG. 8, an additional component (a plate 40) having a smaller circular through hole 44 that matches a sliding diameter of the pinion 18 is required. Here, the pinion 18 slides relative to load bearings 40A, 40B provided on the plate 40.
Further, in the typical spindle 16, spindle end portions 16a and 16b are supported by the circular through hole 14 in the retractor frame 12 so that the spindle 16 can be connected to a mechanism on the exterior of the retractor frame 12. In other words, the circular through hole 14 doubles as a bearing for the spindle 16. Therefore, when the circular through hole in the retractor frame 12 is increased in size, further additional components (bearings or the like for the spindle end portions 16a and 16b, for example) are required to ensure that the end portions of the spindle 16 are supported by the circular through hole 14 in the retractor frame 12, which is problematic in terms of cost.
As another solution, Japanese Examined Utility Model Application Publication No. H7-35805, for example, discloses a safety belt retractor in which side walls of a U-shaped casing open out angularly and a deformation portion, formed by cutting out a bottom plate, is provided to return the opened out side walls to a mutually parallel positional relationship.
According to the safety belt retractor described in Application Publication No. H7-35805, a belt reel and a belt shaft are manufactured as an integrated belt support, and the belt support is inserted up to a hole height between the two side walls of the casing that open out into a V shape in accordance with deformation of the bottom plate. Next, the two side walls are moved to mutually parallel positions by plastically deforming the bottom plate into a flat shape, and thus the safety belt retractor can be manufactured.
In a method of assembling the safety belt retractor described in Application Publication No. H7-35805, the belt reel (the spindle) is inserted from the inside of the U-shaped casing (the retractor frame) rather than from the outside. Therefore, an additional operating step is required to insert the belt reel by applying force to the casing to cause the casing to deform.